Update Changelog for release of version 5.8.1

Author: LaunchDarklyCI

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to the LaunchDarkly Node.js SDK will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org).
 
+## [5.8.1] - 2019-05-13
+### Changed:
+- Changed the package name from `ldclient-node` to `launchdarkly-node-server-sdk`.
+ 
+There are no other changes in this release. Substituting `ldclient-node` version 5.8.0 with `launchdarkly-node-server-sdk` version 5.8.1 (and updating any `require` or `import` lines that referred to the old package name) will not affect functionality.
+
 ## [5.8.0] - 2019-04-06
 ### Added:
 - Generated TypeDoc documentation for all types, properties, and methods is now available online at [https://launchdarkly.github.io/node-server-sdk/](https://launchdarkly.github.io/node-server-sdk/). Currently this will only be for the latest released version.